PHILADELPHIA  Under pressure from federal regulators, Comcast Corp. reversed its stance over hampering online file-sharing by its subscribers and promised Thursday to treat all types of Internet traffic equally.

The Internet service provider said it will collaborate with BitTorrent Inc., the company that invented a more efficient successor to file-sharing services such as Napster and Kazaa, to improve the transmission of large files over the Internet -- and it will eventually stop delaying file transfers based on the specific technology used.

Since user reports of interference with file-sharing traffic were confirmed by an Associated Press investigation in October, Comcast had vigorously defended its practice, most recently at a hearing of the Federal Communications Commission in February.

At issue was whether a service provider like Comcast has the right to control what types of Internet traffic it will let through, block or delay. Comcast said it needs to clamp down on heavy users of Internet bandwidth so others won't be slowed down.

FCC Chairman Kevin Martin said that while he was "pleased" that Comcast has reversed course, he remains concerned that the nation's largest cable company isn't stopping the practice now. Comcast gave itself until year's end.

"While it may take time to implement its preferred new traffic-management technique, it is not at all obvious why Comcast couldn't stop its current practice of arbitrarily blocking its broadband customers from using certain applications," Martin said in a statement.

Martin said the FCC will remain "vigilant" to ensure consumers can access any lawful content online.

Consumer-rights groups say the FCC should still act to protect consumers against other "discriminatory" network-management practices.

"Any arrangements made now would not cover any future developments in blocking, throttling or filtering that any other companies may use," said Gigi Sohn, president of Public Knowledge.

Consumer and "Net Neutrality" advocates have accused Comcast of playing judge and gatekeeper for the Internet by secretly blocking some connections between file-sharing computers. They also accused Comcast of stifling delivery of Internet video, an emerging competitor to its core business.

"This deal is the direct result of public pressure, and the threat of FCC action, against Comcast," said Marvin Ammori, general counsel of Free Press, a media reform group. "But with Comcast's history of broken promises and record of deception, we can't just take their word that the Internet is now in safe hands."

Comcast did not specify how it would manage traffic in the future but said one option was to delay file transfers for the heaviest downloaders, regardless of the specific mechanism used, as the company has been doing.

Comcast said it also was monitoring Time Warner Cable Inc.'s experiment in placing explicit caps on the monthly downloads for new customers in Beaumont, Texas. Subscribers who go over their allotment will pay extra, much like a cell-phone subscriber who uses too many minutes in a month.

But Comcast may be wary about charging certain users more because of competitive pressure, especially after rival Verizon Communications Inc. said recently that such traffic is legitimate and that its FiOS network can handle the flow, said Harold Feld of Media Access Project, a nonprofit advocacy group in Washington, D.C.

BitTorrent and the eDonkey protocol are used for about a third of all Internet traffic, according to Arbor Networks.

The vast majority of file-sharing is illegal distribution of copyright-protected files. But file-sharing is also emerging as a low-cost way of distributing legal content -- in particular, video.

Comcast initially veiled its traffic-management system in secrecy, saying openness would allow users to circumvent it. The company now promises to release details on the new technique and take into account feedback from the Internet community.

Comcast and BitTorrent said they want to work out network management issues privately, without government intervention.

BitTorrent acknowledged service providers have to manage their networks somehow, especially during peak times.

"While we think there were other management techniques that could have been deployed, we understand why Comcast and other ISPs adopted the approach that they did initially," Eric Klinker, BitTorrent's chief technology officer, said in a statement.

Comcast also said that the issue is larger than BitTorrent. It said it was in talks with other parties to find solutions, although the cable company might not have much choice.

Verizon recently announced that by sharing information with Pando Networks, another file-sharing company, it simultaneously sped file-sharing downloads for its subscribers and reduced the strain on its network. AT&T Inc. has been looking at similar collaborations.

But phone companies are better positioned than cable companies to deal with file-sharing traffic because neighbors don't share capacity on phone lines.